Organopolysiloxane polyethers have long been known. They generally consist of an organopolysiloxane having polyoxyalkylene blocks linked terminally and/or laterally. The polyoxyalkylene blocks can be linked to the polysiloxane over SiC or SiOC bonds.
U.S. Pat. No. 3,299,112 is named as being representative of the closest state of the art. This patent discloses a siloxane, which is composed exclusively of
(a) a group of the formula ##STR1## and (b) 1 to 4 groups of the formula ##STR2## wherein the groups and subscripts have the following meanings: a has a value of 0 to 2, PA1 b has a value of 2 to 3, PA1 R is a methyl or ethyl group, PA1 R.sup.1 is an alkyl group with 1 to 4 carbon atoms, PA1 m has a value of 2 to 4, PA1 n has an average value of 4 to 17, PA1 p has an average value of 0 to 5 PA1 the ratio of n: p is at least 2:1, PA1 the sum of n+p has a value of 4 to 17, PA1 the polyoxyalkylene group is linked to the silicon atom of the (a) unit over at least 2 carbon atoms of the C.sub.m H.sub.2m group. PA1 R.sup.2 is a group of the formula (C.sub.m H.sub.2m O--).sub.s R.sup.3, in which
It is shown in the aforementioned U.S. patent that these compounds can be used particularly as wetting agents in aqueous systems.
It has turned out, however, that compounds of this structure have only a limited hydrolysis resistance. Particularly in acidic or basic aqueous solutions, there is splitting of the SiOSi bond and the hydrolysis products can once again be subject to condensation, so that, in the course of the hydrolytic degradation, higher molecular weight organopolysiloxane polyethers, which have a decreased or no wetting action, are formed by a further condensation.